Liquefied gas tanks generally are used to store liquefied petroleum gases such as propane, propylene, butanes and butylenes for use in a plurality of applications including cooking, heating, drying and liquefied petroleum gas fueled engines. More than 18 billion gallons of liquefied petroleum gas are consumed each year in the United States alone. Since these highly flammable gases/liquids are under pressure in liquefied gas tanks, and since an enormous number of liquefied gas tanks are sold every year for use in both industrial and residential applications, there is an essential need for a design of these tanks that reduces the risk of bodily injury caused by tank overfill.
Storage tanks are typically filled to approximately 80-85% of the liquid capacity to allow for the expansion of liquefied petroleum gases and thus proper operation. Regulations and safety requirements have been implemented requiring that liquefied petroleum gas tanks not be filled to 100% capacity but preferably limited to approximately 80% capacity. As a result, a multitude of designs have been proposed to ensure compliance with these requirements. Many of the designs use a float-type system with a flapper portion, similar to a toilet flapper, that acts to close the fill input line when the volume in the tank reaches a specified amount. However, this type of design is disadvantageous, as flapper float mechanisms frequently get dislodged or hung, thereby resulting in an unreliable and less accurate means for preventing the overfilling of liquefied gas tanks.
It is readily apparent that a new and improved overfill prevention device for liquefied gas tanks is needed that is reliable, cost effective and under compliance with the user's local regulations and safety requirements. It is to the provision of such an improvement that the present invention is primarily directed.